1. Field of the Invention
This invention relates to a power transmission belt. More particularly, the invention relates to a power transmission belt which comprises a compression layer and an adhesive rubber layer both of which are formed of a vulcanizate of an ethylene-xcex1-olefin-diene rubber compound and which has a plurality of lord carrying cords formed of polyester fibers embedded in the adhesive rubber layer. The power transmission belt of the invention has excellent dynamic adhesion between the lord carrying cords and the adhesive rubber layer, and hence, it has an extended dynamic belt life. The invention further relates to a process for the production of such a power transmission belt.
2. Description of the Prior Art
In general, a power transmission belt comprises a compression layer and an adhesive rubber layer, and a plurality of lord carrying cords are adhered to and embedded in the adhesive rubber layer. Optionally, the belt has a rubberized canvas or reinforcing fabric on the upper face or the inner face or on the whole surfaces including the side faces.
For the production of a power transmission belt, in particular, a compression layer of the belt, chloroprene rubber or a mixture of hydrogenated nitrile rubber and chlorosulfonated polyethylene has been used heretofore. However, in recent years, an attempt has been made to use ethylene-xcex1-olefin-diene rubber for the production of an adhesive rubber layer as well as a compression layer to meet a demand of xe2x80x9cchlorine freexe2x80x9d products from the standpoint of environmental protection.
However, as known in the art, ethylene-xcex1-olefin-diene rubber has a defect that it is inferior in dynamic properties, in particular, in resistance to fatigue and wear, and tensile strength. In addition, it has poor adhesion to lord carrying cords of polyester fibers. Such being the case, it has been considered difficult to use ethylene-xcex1-olefin-diene rubber to produce power transmission belts in which dynamic properties are important requisites.
The present inventors have made intensive investigation to realize a power transmission belt having excellent dynamic properties which comprises a compression layer and an adhesive rubber layer both of which are formed of ethylene-xcex1-olefin-diene rubber compound and which has a plurality of lord carrying cords formed of polyester fibers (hereinafter referred to polyester fiber cords) bonded to and embedded in the adhesive rubber layer. As results, the inventors have found that the treatment of the polyester fiber cords with a resorcin-formalin-rubber latex adhesive composition wherein the rubber latex in the composition contains at least one of a chlorosulfonated polyethylene and an alkylated chlorosulfonated polyethylene therein as solid components (rubber components) provides excellent dynamic adhesion between the polyester fiber cords and the adhesive rubber layer.
Thus, they have obtained a power transmission belt having excellent dynamic properties which comprises a compression layer and an adhesive rubber layer both of which are formed of ethylene-xcex1-olefin-diene rubber compound and which has a plurality of polyester fiber cords bonded to and embedded in the adhesive rubber layer. Thus, they have completed this invention.
The inventors have further found that the incorporation of a specific metal oxide and a sulfur containing vulcanization accelerator in the resorcin-formalin-rubber latex adhesive composition and the use of such an adhesive composition for treatment of the polyester fiber cords further improves dynamic adhesion between the polyester fiber cords and the adhesive rubber layer even if the polyester fiber cords are dipped in the adhesive composition and dried at a temperature as high as 200xc2x0 C. or more, and accordingly they can manufacture power transmission belts formed of ethylene-xcex1-olefin-diene rubber and having polyester fiber cords embedded therein in a very high productivity.
The invention has been completed to solve the above-mentioned problems in the known power transmission belts formed of ethylene-xcex1-olefin-diene rubber. Accordingly, it is an object of the invention to provide a power transmission belt which comprises a compression layer and an adhesive rubber layer which are formed of ethylene-xcex1-olefin-diene rubber and adhered to each other by vulcanizing together and, which comprises polyester fiber cords adhered to and embedded in the adhesive rubber layer, has and improved dynamic adhesion therebetween.
It is a further object of the invention to provide a process for the production of a power transmission belt as mentioned above.
The invention provides a power transmission belt which comprises a compression layer and an adhesive rubber layer which are adhered to each other by vulcanizing together and which has a plurality of polyester fiber cords embedded in the adhesive rubber layer, wherein the compression layer and the adhesive rubber layer are formed of vulcanizate of an ethylene-xcex1-olefin-diene rubber compound and wherein the polyester fiber cords are adhesion treated with a resorcin-formalin-rubber latex adhesive composition wherein the rubber latex comprises at least one of chlorosulfonated polyethylene and alkylated chlorosulfonated polyethylene in an amount of 50-100% by weight based on the solid components (rubber components) of the rubber latex and adhered to and embedded in the adhesive rubber layer.
The invention further provides a process for production of a power transmission belt which comprises a compression layer and an adhesive rubber layer which are adhered to each other by vulcanizing together and which has a plurality of polyester fiber cords embedded in the adhesive rubber layer, which comprises:
carrying out adhesion treatment of the polyester fiber cords which comprises impregnating the polyester fiber cords with a resorcin-formalin-rubber latex adhesive composition wherein the rubber latex contains at least one of chlorosulfonated polyethylene and alkylated chlorosulfonated polyethylene in an amount of 50-100% by weight based on the solid components (rubber components) of the rubber latex as well as at least one metal oxides and at least one sulfur containing vulcanization accelerators, and heating and drying the resulting polyester fiber cords at a temperature of 200-240xc2x0 C.;
placing the resulting polyester fiber cords between a pair of sheets formed of unvalcanized ethylene-xcex1-olefin-diene rubber compound which are to form an adhesive rubber layer;
laminating the said pair of sheets formed of unvalcanized ethylene-xcex1-olefin-diene rubber compound on a sheet formed of unvalcanized ethylene-xcex1-olefin-diene rubber compound which is to form a compression layer; and
heating the resulting laminate under pressure to vulcanize the laminate in a body to provide the belt, wherein the polyester fiber cords are adhered to and embedded in the adhesive rubber layer.